JEE Main & Advanced Mathematics Definite Integration Question Bank Properties of Definite Integration

  • question_answer
    \[\int_{1/e}^{e}{|\log x|\,dx=}\]                                             [UPSEAT 2001]

    A)                 \[1-\frac{1}{e}\]              

    B)                 \[2\,\left( 1-\frac{1}{e} \right)\]

    C)                 \[{{e}^{-1}}-1\]

    D)                 None of these

    Correct Answer: B

    Solution :

               \[\int_{1/e}^{e}{|\log x|dx=\int_{1/e}^{1}{-\log x\,dx+\int_{1}^{e}{\,\log x\,dx}}}\]                    \[=[x-x\log x]_{1/e}^{1}+[x\log x-x]_{1}^{e}\]                                 \[=(1-0)-\left\{ \frac{1}{e}-\frac{1}{e}(-1) \right\}+e-e+1\]\[=2-\frac{2}{e}=2\left( 1-\frac{1}{e} \right)\].


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